I'm also an active member on SO. There is already more Wordpress tagged posts on SO than on this site, which should actually not be. Yes, SO is used for a dump site, specially by woocommerce questions as they are off topic here. I think the current state of SO is quite bad as there is frankly not enough moderators and active members moderating the site. The current outstanding close vote tally is 12000.
So yes, as not all closevotes are handled immediately and then take months to be handled, many people has moved to SO to drop their junk there. A very large amount of Wordpress questions is poor quality which will definetly get hammered here. So users tend to ignore this site.
Moving low quality and off topic Wordpress questions to SO will make us quilty of plain dumping. And just to note, Wordpress related questions is actually off topic on SO. The problem is, as I said, there are just to few moderating the site, although there are thousands and thousands of 3K + members on the site.
We should not vote to migrate questions that is in some way related to Wordpress, regardless the quality and regardless the question been off topic or not. Close vote poor quality questions and off topic questions and downvote them on your own descresion
We as Wordpress Development has no control over any other site in the SE network, and neither is the up keep of those sites or their content our responsibilty. What is our responsibility is what we decide to migrate to them. All of us with 3K+ reputation has a the opportunity to cast our vote to close, migrate or to leave a question open according to site policy and our own descresion
What questions should be moved
Good quality questions that has nothing to do with Wordpress which falls into scope of SO. These questions are normally well written and clear with relevant code and explanations to what the problem is. They can be easily answered and does bring value to the site it will be moved to
Any question that does not fit the scope of this site and falls completely in scope of SO
What should not be moved and should be closed on WPSE.
Low quality questions that has nothing to do with Wordpress, even if it is in scope of SO. Most off topic questions falls into this category. General programming questions which are unclear, too broad or just don't have enough info to aid someone to answer the question should be close voted and not migrated. If the question don't fit the general idea of how a good question should look like and does not fit the criteria, the migration will probably be rejected by SO, leaving us back to square one
Normally, anything that falls into the too localized category will also be off topic on SO, again in which case the migration might be rejected
-Generally any questions that does not fall into scope of WPSE and SO like general computing, shopping questions and support questions for products and hosting and questions primary based on opinions
As I said before, we are responsible for what we move to other sites, and rejected migration requests does make us look incompetent and like fools. If the user decides to go and ask the same question on SO, it is on him, not us.
I want to close with this, if you are unsure about whether to move or close vote a question, skip it or rather cast a close vote than blindingly casting a vote to migrate the question and dumping a lot of crap on SO which should not be there in the first place